220 to 110 coversion - mistake?

Its really depending on what you use for step down. I use PsaudioP300 powerplant, and absolutly better than straight 220v.

There are any number of transformers being used from the power plant to your home. Adding one more, as long as it is high quality and rated to exceed your requirements won't hurt anything. I wouldn't hesitate if the player is a good deal.

Then again, maybe it can easily be coverted internally to 220VAC and you wouldn't have to worry about it.

As Herman says, many products have wiring provisions so that they are easily reconfigured for different line voltages. Sometimes it is as easy as a switch. Also I am seeing more and more electronic equipment with low power draw (like a CDP) that will operate on any voltage within a wide range. The Behringer DEQ2496, for example, takes 85 to 250 volts, 50 or 60 Hz.

I used an inexpensive transformer from Powerbright with a 220V mid-level CD player and couldn't hear any negative effect. I think I paid less than $30 on ebay. The smallest of them should provide more than enough juice for a CD player, http://www.powerbright.com/transformers.html. Might be worth a try before you go to something more expensive.

What model is the CD player?

Best is to contact the supplier and ask if it can be converted. The vast majority of transformers I have come across allows to be wired for both 220v or 115v, so you may well not require an additional transformer.

Regards
Paul